上一篇介绍了《使用.Net Core与Google Optimization Tools实现员工排班计划Scheduling》，这次将Google官方文档python实现的版本的完整源码献出来，以满足喜爱python的朋友。
顺便可以多展开一下话题，到现在为止的这一套用法，可以应对在线教育中的排班、排课场景， 本质上就是如何合理地设计变量与约束，欢迎交流各种踩坑经历，分享巧妙的应用场景。
from __future__ import print_function
import sys
from ortools.constraint_solver import pywrapcp def main():
# Creates the solver.
solver = pywrapcp.Solver("schedule_shifts") num_nurses = 4
num_shifts = 4 # Nurse assigned to shift 0 means not working that day.
num_days = 7
# [START]
# Create shift variables.
shifts = {} for j in range(num_nurses):
for i in range(num_days):
shifts[(j, i)] = solver.IntVar(0, num_shifts - 1, "shifts(%i,%i)" % (j, i))
shifts_flat = [shifts[(j, i)] for j in range(num_nurses) for i in range(num_days)] # Create nurse variables.
nurses = {} for j in range(num_shifts):
for i in range(num_days):
nurses[(j, i)] = solver.IntVar(0, num_nurses - 1, "shift%d day%d" % (j,i))
# Set relationships between shifts and nurses.
for day in range(num_days):
nurses_for_day = [nurses[(j, day)] for j in range(num_shifts)] for j in range(num_nurses):
s = shifts[(j, day)]
solver.Add(s.IndexOf(nurses_for_day) == j)
# Make assignments different on each day
for i in range(num_days):
solver.Add(solver.AllDifferent([shifts[(j, i)] for j in range(num_nurses)]))
solver.Add(solver.AllDifferent([nurses[(j, i)] for j in range(num_shifts)]))
# Each nurse works 5 or 6 days in a week.
for j in range(num_nurses):
solver.Add(solver.Sum([shifts[(j, i)] > 0 for i in range(num_days)]) >= 5)
solver.Add(solver.Sum([shifts[(j, i)] > 0 for i in range(num_days)]) <= 6)
# Create works_shift variables. works_shift[(i, j)] is True if nurse
# i works shift j at least once during the week.
works_shift = {} for i in range(num_nurses):
for j in range(num_shifts):
works_shift[(i, j)] = solver.BoolVar('shift%d nurse%d' % (i, j)) for i in range(num_nurses):
for j in range(num_shifts):
solver.Add(works_shift[(i, j)] == solver.Max([shifts[(i, k)] == j for k in range(num_days)])) # For each shift (other than 0), at most 2 nurses are assigned to that shift
# during the week.
for j in range(1, num_shifts):
solver.Add(solver.Sum([works_shift[(i, j)] for i in range(num_nurses)]) <= 2)
# If s nurses works shifts 2 or 3 on, he must also work that shift the previous
# day or the following day.
solver.Add(solver.Max(nurses[(2, 0)] == nurses[(2, 1)], nurses[(2, 1)] == nurses[(2, 2)]) == 1)
solver.Add(solver.Max(nurses[(2, 1)] == nurses[(2, 2)], nurses[(2, 2)] == nurses[(2, 3)]) == 1)
solver.Add(solver.Max(nurses[(2, 2)] == nurses[(2, 3)], nurses[(2, 3)] == nurses[(2, 4)]) == 1)
solver.Add(solver.Max(nurses[(2, 3)] == nurses[(2, 4)], nurses[(2, 4)] == nurses[(2, 5)]) == 1)
solver.Add(solver.Max(nurses[(2, 4)] == nurses[(2, 5)], nurses[(2, 5)] == nurses[(2, 6)]) == 1)
solver.Add(solver.Max(nurses[(2, 5)] == nurses[(2, 6)], nurses[(2, 6)] == nurses[(2, 0)]) == 1)
solver.Add(solver.Max(nurses[(2, 6)] == nurses[(2, 0)], nurses[(2, 0)] == nurses[(2, 1)]) == 1) solver.Add(solver.Max(nurses[(3, 0)] == nurses[(3, 1)], nurses[(3, 1)] == nurses[(3, 2)]) == 1)
solver.Add(solver.Max(nurses[(3, 1)] == nurses[(3, 2)], nurses[(3, 2)] == nurses[(3, 3)]) == 1)
solver.Add(solver.Max(nurses[(3, 2)] == nurses[(3, 3)], nurses[(3, 3)] == nurses[(3, 4)]) == 1)
solver.Add(solver.Max(nurses[(3, 3)] == nurses[(3, 4)], nurses[(3, 4)] == nurses[(3, 5)]) == 1)
solver.Add(solver.Max(nurses[(3, 4)] == nurses[(3, 5)], nurses[(3, 5)] == nurses[(3, 6)]) == 1)
solver.Add(solver.Max(nurses[(3, 5)] == nurses[(3, 6)], nurses[(3, 6)] == nurses[(3, 0)]) == 1)
solver.Add(solver.Max(nurses[(3, 6)] == nurses[(3, 0)], nurses[(3, 0)] == nurses[(3, 1)]) == 1)
# Create the decision builder.
db = solver.Phase(shifts_flat, solver.CHOOSE_FIRST_UNBOUND,
solver.ASSIGN_MIN_VALUE)
# Create the solution collector.
solution = solver.Assignment()
solution.Add(shifts_flat)
collector = solver.AllSolutionCollector(solution) solver.Solve(db, [collector])
print("Solutions found:", collector.SolutionCount())
print("Time:", solver.WallTime(), "ms")
print()
# Display a few solutions picked at random.
a_few_solutions = [859, 2034, 5091, 7003] for sol in a_few_solutions:
print("Solution number" , sol, '\n') for i in range(num_days):
print("Day", i)
for j in range(num_nurses):
print("Nurse", j, "assigned to task",
collector.Value(sol, shifts[(j, i)]))
print() if __name__ == "__main__":
main()